Intracellular signaling involves assembly and regulation of multiprotein complexes. These complexes are functional units of signal transduction and are a means by which protein networks carry out tasks within the cell. One mechanism to influence the components, the subcellular localization, and the activity of these complexes, involves scaffold proteins. Scaffold proteins facilitate signal transduction by tethering molecules together and serving as molecular backbones for signaling complex assembly. Recent studies, particularly in the field of signaling kinases, have considerably advanced our understanding of the role that scaffold proteins play within multiprotein complexes in cardiac and other cell types.